Download Physics 101 Problem of the Day

Physics 101 Problem of the Day
Friday Problem: A lead ball is dropped into a lake from a diving board 3.0 m above the water. After
entering the water, it sinks to the bottom with a constant velocity equal to the velocity with which it hit
the water. The lake is 10 m deep.
a. Construct a position versus time graph of the motion.
b. Construct a velocity versus time graph of the motion.
c. Construct an acceleration versus time graph of the motion.
d. How long after it was released did the ball strike the bottom of the lake?
Saturday Problem: The figure below shows the position graph for an object moving along the
horizontal axis. Draw the corresponding velocity graph.
x
parabolic
curve
t
Sunday Problem: The figure below shows a position versus time graph for a moving object. At which
lettered points
a. Is the object moving the fastest?
b. Is the object moving to the left?
c. Is the object speeding up?
d. Is the object slowing down?
e. Is the object turning around?
x
A
B
C
E
F
D
t
Monday Problem: A car traveling at a velocity of 50 m/s takes 175 m to stop after the brakes are
applied. What is the stopping distance if the car is initially traveling at velocity 75 m/s? Assume that
the acceleration due to braking is the same in both cases.
Tuesday Problem: A disoriented physics professor drives 3.25 km north, then 4.75 km west, and then
1.50 km south. Find the magnitude and direction of the resultant displacement, using the method of
components. In a vector addition diagram (roughly to scale) show that the resultant displacement found
from your diagram is in qualitative agreement with the result you obtained using the method of
components.
Wednesday Problem: The catapult of the aircraft carrier USS Abraham Lincoln accelerates an F/A-18
Hornet jet fighter from rest to a takeoff speed of 77.3 m/s (173 mph) in a distance of 93.6 m (307 ft).
Assume constant acceleration.
a. Calculate the acceleration of the fighter in m/s2.
b. Calculate the time required for the fighter to accelerate to takeoff speed.
Thursday morning before
school problem: At a loading
dock a box of mass 200 kg,
initially at rest, is being pushed
across set of frictionless rollers
that are horizontal and 15
meters long.. The person
pulling the box is exerting 20
N of force as shown in the
diagram.
a. What is the weight
of the box?
b. Draw a free body
diagram of forces on the box.
c. Describe the net force on the box in magnitude and direction.
d. What is the acceleration of the box?
e. How long will it take to get the box to the end of the rollers?
f. How fast will the box be traveling at the end of the rollers?
Answers to the above problems
Friday Problem:
c.
x
a
t
Parabolic curve
t
-9.8 m/s2
Linear : Slope = 7.67 m/s
a.
d: The ball settles onto the bottom of the pool
2.08 seconds after being released.
v
t
Linear : Slope = 9.8 m/s2
Linear : Slope = 0 m/s2
b.
Saturday Problem:
v
t
Sunday Problem:
a. C
b. B, C & F
c. B, D & E
d. None of the labeled points
e. E
Monday Problem:
The car traveling at 75 m/s will require 394 meters to come to a stop.
Tuesday Problem:
The resulting displacement of the disoriented physicist is (-4.75 km, 175 km) or equivalently a
vector 5.06 km long at an angle 20.2 degrees North of West.
Wednesday Problem:
a. The fighter jet accelerates at 31.9 m/s2, equivalent to 3.3 g’s.
b. The fighter jet requires 2.42 s to accelerate to takeoff speed.
Thursday Problem:
a. The weight of the box in 1,960 Newtons.
Normal Force (N)
Tension (T)
Weight (mg)
b.
c. The net force on the box is 20 N directed toward the right.
d. The acceleration of the box is 0.1 m/s2 directed to the right.
e. The box will reach the end of the rollers in 17.3 s.
f. The box will be traveling at 1.73 m/s.